Inversion doesn't pretend to be anything it's not. It's a Gears of War knockoff, albeit one with a grab bag of gravity-related features thrown into the mix. Besides the stolen cover system, the "roadie run," and the similar graphics, one of your weapons is even an assault rifle with a scary bayonet attachment.

And that's fine. Gears of War is a great franchise, and a well-made imitation could be an enjoyable experience. A blend of extra gimmicks could give Inversion something special to help it stand out. But unfortunately, even though the developers had a perfect template to work off of, they managed to insert enough design flaws to make Inversion an unworthy buy. Not only does it lack the polish of its big-budget competitor, but it can be downright frustrating to play.

To be fair, the first two-thirds of the seven-hour campaign are fun. This is a game where you and a partner hide behind cover and then pop out and shoot stuff, and it's almost impossible to screw that up. So long as a gamer is slaughtering aliens, not dying unfairly, and not being forced to revive his buddy too often, he's a happy gamer. On my very first sitting, I got more than three hours into the campaign and loved almost every minute of it.

And to spice things up, there are a variety of gravity effects. After some Metroid-style teasing -- you get all the features at the beginning of the game, but then they're taken away -- you end up with a full arsenal of ways to attack your enemies. Using your handy "Gravlink," you can manipulate the Earth's gravitational field however you'd like.

You can reduce gravity to make small items float. Then, in a nod to Half-Life 2's Gravity Gun, you can grab the items and throw them at enemies. There's a ground-pound maneuver for when bad guys get too close, and you can increase gravity to pull down things that are suspended in midair or bring big enemies to their knees. There are also sections scattered through the game that combine the zero-gravity segments of Dead Space with the cover mechanics of Gears of War; the idea is that you float from one piece of cover to another, shooting enemies all the way. And finally, in certain parts of the game the world will flip sideways, Prey-style, so that you're walking on the walls or the ceiling.

As you can tell from the fact that I'm constantly citing other games, very little of this is actually new. And even when Inversion is at its best, it's easy enough to point out the flaws. The graphics, while an admirable attempt to ape the Gears of War style, don't have the detail and polish of their inspiration. The story is a total cliche--aliens are taking over the Earth, and you're a gruff cop who's trying to find his daughter. There are too many cutscenes and too few enemy types. The developers didn't implement the cover system carefully enough. Sometimes the gravity effects can be clumsy to control, and most of the time it's entirely possible to ignore your Gravlink and play Inversion as a standard shooter.

But you know what? None of that changes the fact that Inversion can be fun. If the issues mentioned in the previous paragraph were the only ones, I wouldn't hesitate to recommend Inversion as a rental or a bargain-bin buy.